Double Barrel Sequential Mixing Print E-mail
The Double Barrel® dryer/drum mixer's long mixing chamber and stationary outer shell provide the ability for adding ingredients sequentially. This unique design produces a more consistent mix.
The sequential mixing process is especially well suited for making mixes with RAP.
The sequential mixing process is especially well suited for making mixes with RAP.
Liquid AC enters the drum when aggregates and RAP have reached the proper temperature.
Liquid AC enters the drum when aggregates and RAP have reached the proper temperature.
Mixing paddles ensure that liquid AC thoroughly coats all of the aggregate.
Mixing paddles ensure that liquid AC thoroughly coats all of the aggregate.
Baghouse fines enter the mix last so they don't soak up all of the liquid AC.
Baghouse fines enter the mix last so they don't soak up all of the liquid AC.

Sequential Mixing

To make good mix on a consistent basis, you have to add materials in the right order and at the right time. That's where you can rely on Astec's exclusive sequential mixing process. Ingredients are added to the hot dry aggregate in an order that allows better temperature equalization and even distribution of all particles throughout the mix.

Mix Long For A Better Product

Astec's extraordinarily long mixing chamber allows long mixing times. Long mixing times, together with Astec's sequential mixing, ensure uniform and consistent incorporation of all mix materials. So even if you're dealing with high raw material variance or heavily modified or sticky mixes, the Double Barrel dryer/drum mixer helps you produce homogenous, strong mixes.

Add Recycle First

First in the mixing sequence, recycle material is added to the aggregate in the mixing chamber. Recycle enters into the mixing chamber through a rubber seal. Recycle, which may be RAP, roofing shingles, crumb rubber, or a mixture thereof, is heated by contact with the hot virgin aggregate. When running recycle, the virgin aggregate is heated to higher temperatures than usual.

Coat All Aggregate With AC

At the point where virgin and recycled materials are at the proper temperature and thoroughly mixed, liquid asphalt cement (AC) is injected into the mixing chamber. The 4-foot long AC manifold thoroughly douses the mix. As the mix moves through the mixing chamber, it is continually stirred by mixing paddles.

Embed Fines Into The AC Layer

Baghouse fines and other additives enter the mixing chamber and become embedded in the thick layer of asphalt coating the rock. Astec's sequential mixing keeps fines from soaking up more than their share of AC because the AC has been well distributed before fines are added.